1-1 Understanding Points, Lines, and Planes
Warm Up
Graph each inequality.
1. x ≥ 3
-2
0
2
4
2. 2 ≤ x ≤ 6
0
2
4
3. x < 1 OR x > 0
0
Holt McDougal Geometry
1
6
1-1 Understanding Points, Lines, and Planes
Objectives
Identify, name, and draw points, lines,
segments, rays, and planes.
Apply basic facts about points, lines,
and planes.
Holt McDougal Geometry
1-1 Understanding Points, Lines, and Planes
Vocabulary
undefined term
line
collinear
segment
ray
postulate
Holt McDougal Geometry
point
plane
coplanar
endpoint
opposite rays
1-1 Understanding Points, Lines, and Planes
The most basic figures in
geometry are undefined terms,
which cannot be defined by using
other figures. The undefined
terms point, line, and plane are
the building blocks of geometry.
Holt McDougal Geometry
1-1 Understanding Points, Lines, and Planes
Holt McDougal Geometry
1-1 Understanding Points, Lines, and Planes
Points that lie on the same line are collinear.
K, L, and M are collinear. K, L, and N are
noncollinear. Points that lie on the same
plane are coplanar. Otherwise they are
noncoplanar.
K
L M
N
Holt McDougal Geometry
1-1 Understanding Points, Lines, and Planes
Example 1: Naming Points, Lines, and Planes
A. Name four coplanar points.
A, B, C, D
B. Name three lines.
Possible answer: AE, BE, CE
Holt McDougal Geometry
1-1 Understanding Points, Lines, and Planes
Check It Out! Example 1
Use the diagram to name two planes.
Possible answer:
Plane R and plane ABC.
Holt McDougal Geometry
1-1 Understanding Points, Lines, and Planes
Holt McDougal Geometry
1-1 Understanding Points, Lines, and Planes
Example 2: Drawing Segments and Rays
Draw and label each of the following.
A. a segment with endpoints M and N.
N
M
B. opposite rays with a common endpoint T.
T
Holt McDougal Geometry
1-1 Understanding Points, Lines, and Planes
Check It Out! Example 2
Draw and label a ray with endpoint M that
contains N.
M
Holt McDougal Geometry
N
1-1 Understanding Points, Lines, and Planes
A postulate, or axiom, is a
statement that is accepted as true
without proof. Postulates about
points, lines, and planes help
describe geometric properties.
Holt McDougal Geometry
1-1 Understanding Points, Lines, and Planes
Holt McDougal Geometry